This column is part of a series where Verge staffers post highly subjective reviews of animals. Up until now, we've written about animals without telling you whether they suck or rule. We are now rectifying this oversight.
The sea cucumber doesn't feel fear. It has no memory. In fact, it has no brain (there's a nerve ring around its mouth that appears to be in charge of the extremely limited operation). It doesn't move very quickly — mostly, it creeps across the sea floor.
These animals come in a wide variety of styles, sometimes with frilly tendrils extending from the mouth for catching their microscopic food: algae, tiny animals, general organic nonsense. They play about the same role in the ocean as earthworms do on land, breaking down particles so their nutrients are more available in the ecosystem.
These things are nice, but ultimately not what I am here for. What makes sea cucumbers astonishing is their propensity for shooting their guts out of their butts. Not every species does this — some shoot organs out of their head instead. And of course there are some that don't do this at all.
This process is called evisceration. It's mostly thought to be a defense mechanism, though there's some evidence that sea cucumbers also do it just because — a few species just eviscerate annually. That might be because they eat a lot of nonsense and need to expel their guts to clean them. But they definitely will do it in the presence of danger.
Here's what happens: the body wall softens, as do all the tissues attached to the internal organs to keep them in place. Sea cucumbers belong to a class of animals called echinoderms, and they're pretty rad; one of their features is that they can harden or soften their connective tissue. So once the body wall's softened, the sea cucumber's muscles contract and SPLAT go its internals.
The sea cucumber's muscles contract and SPLAT go its internals
Not all sea cucumbers spew the same stuff, though. Some just eject their viscera but others — tropical sea cucumbers — hit enemies with a jet of Cuverian tubulles, some weird structures that are near the respiratory structures. Cuverian tubulles are shot from near the anus. They're sticky, too; they can slow anything trying to prey on the cukes. And in some species, the Cuverian tubulles are toxic, poisoning the threat.
But what's gone isn't lost forever, because the sea cucumber regenerates the organs they expelled. If they eject their viscera, they regrow that, and regenerate their body walls as well; if it's the Cuverian tubulles, they get new ones. This process varies in length but can take anywhere from a week to 145 days.
In brief: this happens because certain cells in their bodies lose their specialized functions in a process called dedifferentiation. The dedifferentiated cells can then move around the sea cucumber's body and become whatever type of cell is needed to regrow the lost guts. This process is the kind of thing that makes scientists say all kinds of wild things like: "If we figure out how sea cucumbers do it, we might be able to make human cells do it!" They say stuff about regrowing lost limbs and repairing spinal injuries. But that's not what I'm here for.
There are a lot of gross defenses in the animal kingdom. Animals shoot blood out of their eyes, for instance; some beetles send toxic clouds at enemies; they've come up with fecal shields and so on. It's not like the sea cucumber is alone in its nastiness. What I find myself fascinated by is the drama. Imagine the possibilities if I were capable of this! When would I shoot my guts at people? It would be a resounding way to end an argument. I imagine myself as a teenager: my father asks me to turn my music down: I respond by spewing intestine. My teacher asks me to pay attention: intestines again.
Anyway, in case this all didn't upset you enough, you should know that we eat these little buddies. Not just their guts — the whole thing. In fact, they're a high-end snack, and we're eating them in such quantities that some species may go extinct. So here's to the sea cucumber: definitive proof that brains aren't everything.
The Sea Cucumber
Verge Score: 6.5
Lots of color choice
Really good at regeneration
Cleans the ocean floors
Might shoot guts at you